Cardio-respiratory Fitness

The goal of this clinical trial is to learn whether a single session of high-intensity interval exercise (HIIT) affects cognitive performance and brain activity in older adults, and whether cardiorespiratory fitness influences these effects. The main questions it aims to answer are: * Does a single HIIT session change performance on a task-switching test of cognitive flexibility? * Does a single HIIT session change prefrontal brain activity during cognitive testing, as measured by functional near-infrared spectroscopy (fNIRS)? * Do older adults with higher cardiorespiratory fitness show greater cognitive and brain changes in response to HIIT than those with lower fitness? Participants will: * Visit the laboratory on two separate days * Complete a sub-maximal graded exercise test during the first visit to measure cardiorespiratory fitness * Complete a single \~30-minute HIIT cycling session during the second visit * Complete a task-switching cognitive test before and after the HIIT session * Have their brain activity monitored with fNIRS while completing the cognitive tests

The intervention group received 12 weeks of continuous remote intervention combined with health education. The control group only received 12 weeks of continuous health education, and the content and frequency were the same as those of the management group. Both groups received instruction at the beginning of the intervention. The intervention group was given priority to continuous walking/running combined with aerobic exercise and swimming. Five to seven sessions per week for 45 minutes each session. Acclimatizations were performed at an intensity of 40%-49% reserve oxygen uptake (VO2R) from weeks 1 to 4, and exercise was performed at an intensity of 50%-59% VO2R from weeks 5 to 12. 5 minutes each of preparation and grooming activities (including joint movement and stretching) for each exercise. Combined with incremental load resistance exercise 2-3 times a week, 8 movements, 2-3 groups each time, repeated 8-10 times/group, with a 2-min rest between groups. The heart rate, RPE (12-13, "fairly easy" to "somewhat laborious") and exercise bracelet were used to monitor the intensity and amount of exercise. The exercise intervention was usually delivered 1-2 h after a meal. The daily medical supervision in the process of management implementation was carried out by trained sports managers through the doctor terminal of "exercise assistant" to collect and monitor the data of the study subjects.